SEX-DIFFERENCES IN RESPONSE TO CUTANEOUS ANESTHESIA - A DOUBLE-BLIND RANDOMIZED STUDY

The existing literature on experimentally induced pain indicates that there are sex differences, with females displaying greater sensitivity . In epidemiological studies, sex differences are also noted in the pr evalence of a number of pain syndromes, with females reporting more se vere pain, more frequent pain, and pain of longer duration. Complicati ng the interpretation of pain differences between men and women in cli nical samples are reports of sex differences in response to pain-reduc ing medications. Studies in human subjects suggest that women respond better to certain opioid analgesics than men following third molar ext raction, but few studies have assessed sex effects in effectiveness of topical anesthetics. The purpose of this study was to test for sex di fferences in response to a topical anesthetic, Lidocaine, using double blind, placebo controlled experimental methodology, in combination wi th a magnitude matching psychophysical protocol using a pressure algom eter. The subjects were 21 female and 23 male adult volunteers. Twenty -four subjects (12 males and 12 females) were randomly assigned to the Lidocaine condition and 20 subjects were randomly assigned to the pla cebo control condition (9 males and 11 females). The effect size acros s sex for subjects in the Lidocaine treatment condition on the respons e bias variable was large indicating the males rated the stimuli as le ss painful than the females. Sex differences were not observed for dis criminability in the Lidocaine treatment condition. This study did not show sex differences in the placebo condition. These results are part icularly interesting in light of previous work that has shown similar pain stimuli (pressure pain) to be the stimulation most sensitive to s ex differences. Results of this study suggest that the protocol employ ed (pressure pain stimulus with magnitude matching task) is sensitive to both anesthetic treatment and sex differences and represents an imp rovement in pain assessment methodology for use in experimental studie s and in the clinic. (C) 1998 International Association for the Study of Pain. Published by Elsevier Science B.V.